MM_BSC_SOLNS_2004

# MM_BSC_SOLNS_2004 - CM0340 SOLUTIONS CARDIFF UNIVERSITY...

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CM0340 SOLUTIONS 1 CARDIFF UNIVERSITY EXAMINATION PAPER SOLUTIONS Academic Year: 2003-2004 Examination Period: Autumn 2003 Examination Paper Number: CM0340 Examination Paper Title: Multimedia Duration: 2 hours Do not turn this page over until instructed to do so by the Senior Invigilator. Structure of Examination Paper: There are four pages. There are four questions in total. There are no appendices. The maximum mark for the examination paper is 100% and the mark obtainable for a question or part of a question is shown in brackets alongside the question. Students to be provided with: The following items of stationery are to be provided: One answer book. Instructions to Students: Answer THREE questions. The use of translation dictionaries between English or Welsh and a foreign language bearing an appropriate departmental stamp is permitted in this examination.

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CM0340 SOLUTIONS 2 1. (a) What does Nyquist’s Sampling Theorem state? In order to effectively sample a waveform the sampling frequency must be at least twice that of the highest frequency present in the signal 2 Marks --- Bookwork (b) What are the implications of Nyquist’s Sampling Theorem for multimedia data? Sampling frequency affects the quality of the data ---- higher frequency equals better sampling hence representation of the underlying signal (given fixed frequency range of signal) Sampling frequency affects size of digitized data --- higher frequency means more samples therefore more data. 4 (2 marks each above) Marks --- Bookwork
CM0340 SOLUTIONS 3 (c) For each of the following media types, graphics, images, audio and video, briefly discuss how Nyquist’s Sampling Theorem affects the quality of the data and the form in which sampling effects manifest themselves in the actual data. Graphics o Quality: Not an issue with vector graphics o Sampling Artifact: Rendering may lead to Aliasing effect in lines etc Images o Quality: Image size decreases so less detail or sampling artifacts o Sampling Artifact: Aliasing effect in blocky images Audio o Quality: Lack of clarity in high frequencies, telephonic voices at low sampling frequencies o Sampling Artifact: Digital noise present in signal, loss of high frequencies or poor representation of high frequencies give audio aliasing (should be filtered out before sampling) Video o Quality: Video Frame size decreases so less detail or sampling artifacts, motion blur or loss of motion detail o Sampling Artifact: Aliasing effect in frame images, jittery motion tracking etc. 12 (3 Marks per media type) Marks --- Unseen: Extended reasoning on a few parts of course

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CM0340 SOLUTIONS 4 (d) Calculate the uncompressed digital output, i.e. data rate, if a video signal is sampled using the following values: 25 frames per second 160 x 120 pixels True (Full) colour depth True color = 24 bits (3 bytes) per pixel So number of bytes per second is 3*160*120*25 = 144000 bytes or 1.37 Mb 3 Marks --- Unseen: Application of basic knowledge
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## This note was uploaded on 01/26/2012 for the course CM 0340 taught by Professor Davidmarshall during the Fall '09 term at Cardiff University.

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MM_BSC_SOLNS_2004 - CM0340 SOLUTIONS CARDIFF UNIVERSITY...

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